A current sensor is a typical application of a magnetic sensor. The principle thereof is making a detection current pass through a primary coil, generating a detection magnetic field therefrom, then sensing the intensity of the magnetic field using a magnetic sensor, and converting the detected magnetic field into a voltage signal for output, thereby establishing a relationship between the input current and the output voltage signal. An integrated current sensor integrates a magnetic sensor and a primary coil and packages them into a current sensor chip. At present, there are two types of typical integrated current sensors. FIG. 1 shows an AAV003 integrated current sensor 1 of the NVE company. A measured current thereof may be up to 5 A, and magnetic sensors 2 thereof are of a GMR type and form a full-bridge gradient sensor. A primary coil 3 is U-shaped, where the primary coil 3 includes two straight strips 31 and 32, and bridge arms 22 and 21 of two sets of magnetoresistive sensor units making up a full bridge are respectively placed below the straight strips 31 and 32. As shown in FIG. 2, bridge arms R0 and R1 correspond to the straight strip 31, bridge arms R3 and R4 correspond to the straight strip 32, a magnetic field generated by the straight strip 31 near the positions of R0 and R1 is Hx1, a magnetic field generated by the straight strip 32 near the positions of R3 and R4 is Hx2, and the two magnetic fields have opposite magnetic field directions but are of the same magnitude. The GMR magnetoresistive sensor units R0, R1, R3, and R4 have a same X magnetic field sensitive direction. A bridge connection structure is as shown in FIG. 3, which is a typical full-bridge differential structure, and two output signal ends are V+ and V− respectively.
FIG. 4 shows another type of integrated current sensor, i.e., a TL14970 integrated current sensor 4 of the Infineon company. A measured current thereof ranges from −50 A to +50 A. The integrated current sensor includes a Hall gradient sensor 5, a linear strip primary coil 6, a ceramic separator 7 for isolating the Hall gradient sensor 5 from the linear strip primary coil 6, and a signal output interface 8, where the stripped primary coil 6 and the signal output interface 8 are both made of a lead frame material. In addition, the Hall gradient sensor 5 is directly placed above the linear strip primary coil 6. FIG. 5 is a planar structural diagram of an integrated current sensor including a lead frame primary coil. Hall sensor units R0 and R1 are symmetrically located on two sides of a center line 9 of the primary coil 6 respectively. Z-direction magnetic field components generated by the current in the primary coil 6 at the position of R0 and the position of R1 are Hz1 and Hz2 respectively, which are of the same magnitude but in opposite directions. A differential connection structure thereof is as shown in FIG. 6, and an intermediate output signal of the half-bridge structure is Vout.
Upon comparison, it can be seen that, different from the U-shaped primary coil that requires two straight wires having opposite currents to realize a differential magnetic field, the linear strip primary coil has a larger width and is made of a lead frame material, and thus it can permit a greater current pass therethrough making it more useful for large current measurement.
As compared with Hall and GMR sensors, TMR sensors have higher magnetic field sensitivity, lower power consumption, small size, and other advantages. Therefore, by use of TMR sensors, an integrated current sensor with higher precision can be prepared. On the other hand, by use of a lead frame with a linear strip primary coil, measurement of higher-amplitude currents can be realized. In combination with the advantages of the TMR sensors and the lead frame primary coil, a new type of integrated current sensor having high precision and a larger current range can be achieved.